- small (length < 5) arrays with shape and stride information had to be
  memcpy'd to the GPU before every kernel call
- instead of passing the information as arrays, the single elements are
  passed
- leads to more function arguments, but simplifies GPU kernel calls

-> changes in all backends required

- removed warnings
- added flake8 as CI target

- test run again
- notebooks not yet

- Previously sympy.Eq was used to represent assignments. However Eq
  represents equality not assignment. This means that sometimes sympy
  "simplified" an equation like a = a  to True,
-> replaced sp.Eq by pystencils.Assignment everywhere
- renamed EquationCollection to AssignmentCollection

- single function to create kernel for specified target
- data type creation from string - reuse numpy functionality
- bugfixes in dot display

Testcases test_mu_equivalence, test_phi_equivalence are passing.

Fixed a severe bug. Renamed makePythonFunction of the llvm backend.
Deleted code duplicity.

Fixed function bug.

Added LLVM: CodePrinter and a compiler
Updated data_types
Added tests
Added jupyter notebooks
Fixed bugs
Restructured transformation functions

- renaming because of clashes with types.py from other packages

Move my llvm demo notebook in the correct folder